Tensioner

ABSTRACT

The invention comprises a self-contained mechanical belt tensioner that produces damping which is a function of the applied hubload through the effect of frictional forces derived from the sliding action of mutually opposing wedges. A first wedge or conical piston is contained within a housing. The conical piston cooperates with a second or conical wedge. A surface of the conical wedge slides on the inner surface of the housing. The conical wedge is expandable in a direction normal to the inner surface of the housing. A spring urges the conical wedge into engagement with the conical piston. As the pulley is loaded, as with an impulse load, the piston will move into the conical wedge. This, in turn, will cause the conical wedge to expand against the inner surface of the housing. The expansion of the conical wedge in the housing will increase the frictional force between the conical wedge and the housing. This will have the effect of damping movements of the conical piston and, in turn, of the pulley. The greater the impulse, then the greater the expansion of the conical wedge. This increases the resultant frictional force resisting movement between the conical wedge and the housing. As the load moves toward a minimum, the frictional force is abated to a low level allowing ease of retraction of the piston.

REFERENCE TO RELATED APPLICATIONS

[0001] This divisional application claims priority from U.S.non-provisional application Ser. No. 09/549,258.

FIELD OF THE INVENTION

[0002] The invention relates to tensioners, more particularly totensioners that are spring biased, wedge actuated belt tensioningdevices having damping and used with belts for vehicle accessory drives.

BACKGROUND OF THE INVENTION

[0003] Most engines used for automobiles and the like include a numberof belt driven accessory systems which are necessary for the properoperation of the vehicle. The accessory systems may include analternator, air conditioner compressor and a power steering pump.

[0004] The accessory systems are generally mounted on a front surface ofthe engine. Each accessory would have a pulley mounted on a shaft forreceiving power from some form of belt drive. In early systems, eachaccessory was driven by a separate belt that ran between the accessoryand the crankshaft. With improvements in belt technology, singleserpentine belts are now used in most applications. Accessories aredriven by a single serpentine belt routed among the various accessorycomponents. The serpentine belt is driven by the engine crankshaft.

[0005] Since the serpentine belt must be routed to all accessories, ithas generally become longer than its predecessors. To operate properly,the belt is installed with a pre-determined tension. As it operates, itstretches slightly. This results in a decrease in belt tension, whichmay cause the belt to slip. Consequently, a belt tensioner is used tomaintain the proper belt tension as the belt stretches during use.

[0006] As a belt tensioner operates, the running belt may exciteoscillations in the tensioner spring. These oscillations areundesirable, as they cause premature wear of the belt and tensioner.Therefore, a damping mechanism is added to the tensioner to damp theoscillations.

[0007] Various damping mechanisms have been developed. They includeviscous fluid based dampers, mechanisms based on frictional surfacessliding or interaction with each other, and dampers using a series ofinteracting springs.

[0008] Representative of the art is U.S. Pat. No. 4,402,677(1983) toRadocaj which discloses a tensioner having an L-shaped housing. A pairof cam plates having camming surfaces are slideably mounted in theL-shaped housing. A compression spring biases the camming plates intosliding engagement with each other. The included angle of the cammingsurfaces equal 90° with the angle of a first camming surface beinggreater than the angle of a second camming surface.

[0009] Also representative of the art is U.S. Pat. No. 5,951,423(1999)to Simpson which discloses a mechanical friction tensioner having springloaded wedge-shaped blocks and friction damping. The tensioner has awedge-shaped piston that interacts with spring biased wedge-shapedblocks. As the piston moves inward the wedge-shaped blocks are pushedoutward to provide friction damping.

[0010] The prior art devices rely on springs or other components, eachoriented on axes that are set at a pre-determined angle to each other.They also rely on a plurality of springs to properly operate the dampingcomponents and to urge the belt pulley into contact with a belt. Theprior art does not teach a damping components that operate coaxially.Further, the prior art does not teach use of an expandable camming body.Nor does it teach the use of an expandable camming body that expandsradially. Nor does it teach the use of an expandable camming body thatexpands radially in response to movement against a piston. Nor does itteach the use of an expandable camming body that expands radially inresponse to movement against a tapered piston.

[0011] What is needed is a tensioner having a coaxial piston and cammingbody operating coaxially. What is needed is a tensioner having anexpandable camming body. What is needed is a tensioner having anexpandable camming body that is radially expandable. What is needed is atensioner having an expandable camming body that is radially expandablein response to movement against a piston. What is needed is a tensionerhaving an expandable camming body that expands radially in response tomovement against a tapered piston. The present invention meets theseneeds.

SUMMARY OF THE INVENTION

[0012] The primary aspect of the invention is to provide a tensionerhaving a coaxial tapered piston and camming body.

[0013] Another aspect of the invention is to provide a tensioner havingan expandable camming body.

[0014] Another aspect of the invention is to provide a tensioner havingan expandable camming body that is radially expandable.

[0015] Another aspect of the invention is to provide a tensioner havingan expandable camming body that is radially expandable in response tomovement against a piston.

[0016] Another aspect of the invention is to provide a linear tensionerhaving an expandable camming body that expands radially in response tomovement against a tapered piston.

[0017] Other aspects of the invention will be pointed out or madeobvious by the following description of the invention and theaccompanying drawings.

[0018] The invention comprises a self-contained mechanical belttensioner that produces damping which is a function of applied hubloadthrough the effect of frictional forces derived from the sliding actionof mutually opposing wedges. A conical piston is contained within ahousing. The conical piston cooperates with a conical wedge or cammingbody. The conical wedge slides on the inner surface of the housing. Theconical wedge is radially expandable in a direction normal to thehousing. A spring urges the conical wedge into engagement with theconical piston. As the pulley is loaded, as with an impulse load, thepiston will move into the conical wedge. This, in turn, will cause theconical wedge to radially expand against the inner surface of thehousing. The expansion of the conical wedge in the housing will increasethe frictional force between the conical wedge and the housing. Thiswill have the effect of damping movements of the wedge and conicalpiston. The greater the impulse, then the greater the expansion of theconical wedge. Hence, this increases the resultant frictional forceresisting movement between the conical wedge and the housing. As theload moves toward a minimum, the camming body radially contracts and thefrictional force is abated to a low level allowing ease of retraction ofthe piston.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and form apart of the specification, illustrate preferred embodiments of thepresent invention, and together with a description, serve to explain theprinciples of the invention.

[0020]FIG. 1 is a cross-sectional view of the invention.

[0021]FIG. 2(a) is a top plan view of the wedge through section 2 a-2 ain FIG. 3.

[0022]FIG. 2(b) is a side elevation view of the wedge through section 2b-2 b in FIG. 3.

[0023]FIG. 3 is a side cross-section view of the damping section of theinvention:

[0024]FIG. 4 is a perspective view of the wedge.

[0025]FIG. 5 is a perspective view of the piston 14.

[0026]FIG. 6 is a perspective view of the housing 1.

[0027]FIG. 7(a) is a schematic free body diagram of the dampingmechanism during a compression stroke.

[0028]FIG. 7(b) is a schematic free body diagram of the dampingmechanism during a return stroke.

[0029]FIG. 8 is a cross-sectional view of a first alternate embodimentof the invention.

[0030]FIG. 9 is a plan view of the wedge for the alternate embodiment.

[0031]FIG. 10 is a cross-sectional view of the housing for the alternateembodiment:

[0032]FIG. 11 is a cross-sectional view of a second alternate embodimentof the invention.

[0033]FIG. 12 is a cross-sectional view of a third alternate embodimentof the invention.

[0034]FIG. 13 is a cross-sectional view along axis A-A of a fourthalternate embodiment of the invention.

[0035]FIG. 14 is a cross-sectional view along axis A-A of a fifthalternate embodiment of the invention.

[0036]FIG. 15 is a plan view of a tensioner.

[0037]FIG. 16 is a perspective exploded view of the damping mechanismfor an alternate embodiment.

[0038]FIG. 17 is an end plan view of the wedge for an alternateembodiment.

[0039]FIG. 18 is an end plan view of the tube of an alternateembodiment.

[0040]FIG. 19 is an end plan view of the wedge for an alternateembodiment.

[0041]FIG. 20 is an end plan view of the tube of an alternateembodiment.

[0042]FIG. 21 is an exploded view of the wedge and tube for an alternateembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0043]FIG. 1 is a cross-sectional view of the invention. A lineartensioner is shown having a damping section that is distinct from thepivot/pulley section. Housing 1 contains the damping components for thetensioner. Housing 1 in the preferred embodiment is cylindrical.However, housing 1 may have any shape generally compatible with theoperation described herein. Pivot arm 3 is pivotably connected tohousing 1. Pulley 8 is journaled to pivot arm 3. Pulley 8 engages a beltB to be tensioned. Adjuster or adjusting screw 7 having a flange isthreaded into an end of housing 1 and is used to adjust or fine tune thespring preload force and hence the damping force by turning clockwise orcounterclockwise as required by a user.

[0044] Compressible member or spring 6 bears on wedge 13. Wedge orcamming body 13 comprises a tapered or conical hole 15. Wedge outersurface 16 is slidingly engaged with housing inner surface 17. Wedgeouter surface 16 may comprise a nonmetallic material, such as plastic orphenolic. Piston 14 comprises a cylindrical shape. End 19 of piston 14has a tapered or frustoconical shape that cooperates with hole 15 inwedge 13. End 20 of piston 14 opposite the conical end cooperates withbearing point 18. Bearing point 18 allows pivot arm 3 to press upon theend 20 of piston 14 without undue binding.

[0045]FIG. 2(a) is a top plan view of the wedge through section 2 a-2 ain FIG. 3. Wedge or camming body 13 comprises slots 40, 41. Slots 40project from an outer surface of the wedge toward the hole 15. Slots 41project from hole 15 toward an outer surface of the wedge. Slots 40, 41allow wedge 13 to radially expand and contract, shown as bi-directionalarrow E, as the tensioner operates according to the followingdescriptions. One should note that although the surface 16 is shown assmooth and of circular shape in this FIG. 2a, surface 16 may have othershapes or profiles as described in the other figures described in thisspecification.

[0046]FIG. 2(b) is a side elevation view of the wedge through section 2b-2 b in FIG. 3. Slots 40 extend from a first surface 44 of the wedgeand slots 41 extend from an opposing surface 45 of the wedge as comparedto the first surface. Slots 40, 41 further comprise holes 42, 43respectively, which allow the wedge sides to expand and contract withoutcausing cracking or failure of the wedge at each slot end.

[0047]FIG. 3 is a side cross-section view of the damping section of theinvention as described in FIG. 1. Movement of the pivot arm 3 drivespiston 14 into the wedge 13. Spring 6 biases wedge 13 into piston 14. Inoperation, piston 14 is driven into wedge 13, thereby expanding wedge 13against surface 17. The frictional force between wedge surface 16 andsurface 17 damps the motion of the wedge and thereby the motion of thepiston 14. Note that although surface 17 is shown as cylindrical in thisFIG. 3, surface 17 may have other shapes or profiles as shown in theother figures described in this specification.

[0048]FIG. 4 is a perspective view of the wedge. Camming body or wedge13 comprises surface 16 that slidingly engages inner surface 17 ofhousing 1. Wedge 13, and more particularly, surface 16 may have apleated or star shape. This shape serves to increase the frictionalforces, between surface 16 and inner surface 17. Inner surface 17 andsurface 16 may have any shape, so long as they are able to be properlymated to maximize surface contact between them and are able to sliderelative to each other along a common axis, A, without binding.

[0049]FIG. 5 is a perspective view of the piston 14. Piston 14 comprisestapered end 19 and end 20. Tapered end 19 cooperates with tapered hole15 in wedge 13. Bearing point 18 bears upon end 20. Although surface 16is star shaped, tapered end 19 and tapered hole 20 each have a conicalor frustoconcical shape. In the preferred embodiment, piston 14comprises steel, although any durable material having similar frictionaland compressive properties would be acceptable.

[0050]FIG. 6 is a perspective view of the housing 1. Housing 1 comprisesinner surface 17. Inner surface describes a pleated or star profile inorder to cooperate with surface 16 of wedge 13. In the preferredembodiment, housing 1 is constructed of aluminum, although any durablematerial having similar frictional and strength bearing properties wouldbe acceptable. Housing 1 may b attached to a base (not shown) as part ofa tensioner assembly as shown in FIG. 1.

[0051] The operation of the tensioner is as follows. Reference is madeto FIG. 7(a), a schematic free body diagram of the damping mechanismduring a compression stroke. During the compression stroke, the hubloadHC bears upon piston 14, which acts upon wedge 14, shown as R. Themovement of the tapered end 19 into hole 15 causes an outercircumference of wedge 13 to increase and press surface 16 against theinner surface 17. Due to friction between the sides of the tapered end19 and the sides of the tapered hole 15, movement of piston 14 indirection C acts to move wedge 13 also in direction C. However, themovement of wedge 13 in direction C is resisted by spring 6, the springforce being depicted as F_(s). A normal force is formed between thesides of the tapered end 19 and the sides of the tapered hole 15, and isresolved into normal forces between them, N_(1C) and N_(2C). Africtional force acts between the sides of the tapered end 19 and thesides of the tapered hole 15 as well as between the sides of the wedgeand the inner surface of the housing. A frictional force resisting themotion of the wedge in the housing is formed. These forces are μN_(1C)and μN_(2C). This force is additive with the spring force, F_(s), aseach acts in the same direction. As the hubload increases, so increasesHC. An increase in HC increases N_(1C) and N_(2C) until wedge 13 startsmoving, which in turn increases the friction forces μN_(1C) and μN_(2C)resisting movement of the wedge in the housing. It should be noted thatthere is no further substantive increase in N_(1C) and N_(2C) when wedge13 moves.

[0052] On the return stroke, depicted in FIG. 7(b) a free body diagramof the damping mechanism during the return stroke, the hubload isdiminished. Once the hubload HR becomes less than the spring force F_(s)minus friction μN_(1R), the wedge will be pushed in direction B. Thenormal forces, N_(1R) and N_(2R) are less than N_(1C) and N_(2C).Further, the friction force vector is in the opposite direction ascompared to the compression stroke, μN_(1R) and μN_(2R). This frictionalforce resists the effort of the spring to move the wedge in direction B.The hubload HR required to keep the blocks in static equilibrium isreduced. Since the hubload is reduced, the frictional forces between thewedge and the inner surface of the housing are correspondingly reduced.Hence, the damping, or frictional force, is greater during thecompression stroke than during the return stroke. Therefore, thetensioner exhibits asymmetric damping.

[0053] An alternate embodiment is depicted in FIG. 8. Damper 100comprises a cylinder slidingly engaged with another cylinder. Outer tubeor housing 101 slidingly engages tube 108. Cap 105 is attached to tube101. Cap 110 is attached to tube 108. Spring 102 extends between cap 105and end of tube 108, thereby urging the tubes apart. Plastic liner 106facilitates movement between outer tube 101 and tube 108. Piston 111 isaffixed to cap 110 and is parallel to a major axis of the tubes 101,108. Wedge 109 slidingly engages an inner surface 112 of tube 108.Piston tapered end 104 engages tapered hole 113 in wedge 109. Wedge 109is urged into contact with piston 111 by spring 107. Biasing member orspring 107 bears upon cap 110 and wedge 109. Cap 110 may be affixed to amounting surface, such as on a tensioner body as described in FIG. 1.

[0054] In operation, cap 105 moves in direction C during a compressionstroke. It moves in direction R during a return stroke. The detaileddescription of operation is set forth in FIG. 7(a) and FIG. 7(b).Further, during the compression stroke, the wedge 109 is pushed indirection C, thereby causing behavior as described in FIG. 7(b) for thereturn stroke. The damping force in is increased during the returnstroke in direction R since the inner surface 112 is moving in a mannerso as to press wedge 109 into the tapered end 119 of piston 104. This isdescribed in FIG. 7(a). One skilled in the art will appreciate that themechanism described in this FIG. 8 depicts a damping mechanism that isoperable in various applications including a belt tensioner with apulley.

[0055]FIG. 9 is a detail of the wedge in FIG. 8. Wedge 109 comprisessplines or pleats 114. Splines 114 cooperatively engage a like shape onthe inner surface 112 of tube 101 as shown in FIG. 10. Wedge 109 mayhave radially extending slots 115 that facilitate expansion of the wedgeagainst the inner surface 112. Wedge splines 114 may comprise anonmetallic material, such as plastic or phenolic.

[0056]FIG. 10 is an end view of the outer tube. Tube 101 comprises innersurface 112. Surface 112 describes a pleated or splined profile thatcooperatively engages splines 114 on wedge 104. Surface 112 and splines114 each comprise materials that create a desired frictionalcoefficient. For example, the splines 114 may comprise a plastic,phenolic or non-metallic material while surface may comprise likematerials. The preferred embodiment comprises a non-metallic material onsplines 114 and a metallic material on surface 112, as well as surface112 (FIG. 10), surface 212 (FIG. 11, 18), surface 312 (FIG. 20).

[0057]FIG. 11 is a cross-sectional view of a second alternate embodimentof the invention. In this alternate embodiment, spring 202 is containedwithin tube 201. Damper 200 comprises a cylinder slidingly engagedwithin another cylinder. Outer tube 201 slidingly engages tube 208. Cap205 is attached to tube 208. Cap 210 is attached to tube 201. Biasingmember or spring 202 extends between tube 208 and cap 210, therebyurging them apart. Plastic liner 206 facilitates sliding movementbetween outer tube 201 and tube 208. One end of piston 211 is affixed tocap 210 and is parallel to a major axis of the tubes 201, 208. Wedge 209slidingly engages an inner surface 212 of tube 208. Piston tapered end204 engages tapered hole 213 in wedge 209. Wedge 209 is urged againsttapered end 204 by compressible member or spring 207. Spring 207 bearsupon cap 210 and wedge 209. Cap 210 is affixed to a mounting surface,such as on a tensioner body as described in FIG. 1. One skilled in theart will appreciate that the mechanism described in this FIG. 11 depictsa damping mechanism that is operable on other applications including atensioner with a pulley.

[0058] In operation, cap 205 moves in direction C during a compressionstroke. Cap 205 moves in direction R during a return stroke. Thedetailed description of operation is set forth in FIGS. 7(a), 7(b) andFIG. 8.

[0059]FIG. 12 depicts another alternate embodiment of the damper 300.The elements are generally as described in FIG. 11 with the followingdifferences; washer, ring or bearing surface 308 is affixed to piston211 at a pre-determined point. Bearing surface 308 extends normally tothe piston axis D. Compressible member or spring 307 bears on thebearing surface 308. The other end of spring 307 bears on camming bodyor wedge 309. Wedge 309 is of substantially the same form as wedge 209in FIG. 11. One skilled in the art will appreciate that the mechanismdescribed in this FIG. 12 depicts a damping mechanism that is operableon other applications including a tensioner with a pulley.

[0060] Reference to FIG. 11 and FIG. 12 also illustrates the change inlength L₁ and L₂ as the invention operates. Lengths increase during thereturn stroke R (L₂) and decrease during the compression stroke C (L₁).

[0061]FIG. 13 is a cross-sectional view along axis A-A of yet anotheralternate embodiment of the invention. First housing or cap 405comprises first housing surface or side 408. Second housing or tube 401further comprises outer surface 412. Side 408 describes a conical formhaving an angle α to the major axis A in the range of 0° to 30°. Side408 may have any form required by a user, including pleated. Wedge 409slides between side 408 and outer surface 412. Spring 402 urges wedge409 into contact with side 408 and outer surface 412. As wedge 409 isurged against surface 412, it is radially compressed. Radial compressionof wedge 409 occurs due to the presence of the slots as described inFIG. 2 and FIG. 21. Spring 402 bears on base 410, which is affixed totube 410. Cap 405 moves in direction C during a compression stroke andin direction R during a return stroke. A load L may be applied to thedevice at bearing point 418. One skilled in the art will appreciate thatthe mechanism described in this FIG. 13 depicts a damping mechanism thatis operable on other applications including a tensioner with a pulley.

[0062]FIG. 14 is a cross-sectional view along axis A-A of yet anotheralternate embodiment of the invention. First housing or tube 501comprises first housing surface or side 508 and end 510. Side 508describes a conical form having an angle β to the major axis A in therange of 0° to 30°. Side 508 may have any profile required by a userincluding pleated. Wedge 509 slides between first housing surface orside 508 and outer surface 516 of piston 514. Wedge 509 has the sameform as shown in FIG. 21 for wedge 409. Body 519 and surfaces 516 havethe same form as shown in FIG. 21 for surface 412. Spring 502 bears onend 510 and piston 514. Spring 502 resists an axial movement of piston514. Compressible member or spring 502 also bears on base 510 againstpiston 514. Compressible member or spring 507 urges wedge 509 intocontact with side 508 and outer surface 516 of piston 514. As wedge 509is urged against surface 516, it is radially compressed. Radialcompression of wedge 509 occurs due to the presence of the slots asdescribed in FIG. 2 and FIG. 21. Piston 514 moves in direction C duringa compression stroke and in direction R during a return stroke. An axialload L may be applied to the device at bearing point 518. One skilled inthe art will appreciate that the mechanism described in FIG. 14 depictsa damping mechanism that is operable on other applications including atensioner with a pulley.

[0063]FIG. 15 is a plan view of a tensioner damper assembly. Damper 600as described in the foregoing FIGS. 8, 11-14 is shown connected to anidler pulley 610 by shaft 620. Shaft 620 may be connected to a base (notshown) that connects the idler to tracks 615. Idler 610 slides alongparallel tracks 615. Belt B is trained about idler 610.

[0064]FIG. 16 is a perspective exploded view of the damping mechanismfor an alternate embodiment. FIG. 16 generally describes the arrangementof the damping mechanism for the embodiments depicted in FIGS. 8, 11 and12. The numbers in FIG. 16 relate to FIG. 8. Surfaces 114 slidinglyengage surfaces 112. Tapered end 104 engages hole 113. Slots 115 allowwedge 109 to radially expand as tapered end 104 moves axially into wedge109. Wedge 109 may comprise a nonmetallic material, such as plastic orphenolic.

[0065]FIG. 17 is an end plan view of the wedge for an alternateembodiment. The alternate embodiment is depicted in FIG. 11. Wedgesplines 214 may comprise a nonmetallic material, such as plastic orphenolic.

[0066]FIG. 18 is an end plan view of the tube of an alternateembodiment. The alternate embodiment is depicted in FIG. 11.

[0067]FIG. 19 is an end plan view of the wedge for an alternateembodiment. The alternate embodiment is depicted in FIG. 12. Wedgesplines 314 may comprise a nonmetallic material, such as plastic orphenolic.

[0068]FIG. 20 is an end plan view of the tube of an alternateembodiment. The alternate embodiment is depicted in FIG. 12.

[0069]FIG. 21 is an exploded view of the wedge and tube for an alternateembodiment. The embodiment is depicted in FIG. 13. FIG. 21 alsogenerally depicts the arrangement of the wedge 509 and the pistonsurfaces 516 for the embodiment depicted in FIG. 14. Slots 415 allowwedge 409 to radially compress against surfaces 412. Wedge 409 maycomprise a nonmetallic material, such as plastic or phenolic.

[0070] Although a single form of the invention has been describedherein, it will be obvious to those skilled in the art that variationsmay be made in the construction and relation of parts without departingfrom the spirit and scope of the invention described herein.

We claim:
 1. A tensioner comprising: a housing having a housing surface;a wedge having a wedge surface that slidingly engages the housingsurface, the wedge further describing a hole; a piston having a firstend cooperatively engaging the hole; a pivot arm having a pulleyjournaled to an end, the pivot arm pivotably mated to a surface andhaving a second end bearing on an end of the piston opposite the firstend; and a compressible member biasing the wedge toward the piston,whereby movement of the wedge against the first end causes the wedge toradially expand against the housing surface thereby damping a movementof the piston.
 2. The tensioner as in claim 1, wherein: the wedge holecomprises a frustoconcical hole; and the piston first end comprises afrustoconcical shape that cooperatively engages the frustoconical hole.3. The tensioner as in claim 2, wherein the wedge further comprises: atleast one slot, the slot oriented so the circumference of the wedge isradially expandable in response to a movement against the piston firstend.
 4. The tensioner as in claim 3, further comprising: an adjusterbearing on an end of the compressible member and the housing whereby acompressible member preload may be changed.
 5. The tensioner as in claim4, wherein: the wedge outer surface further describes a pleated form;and the inner surface further describes a pleated form that cooperateswith the pleated form of the wedge outer surface.
 6. The tensioner as inclaim 5, wherein the housing further comprises a cylinder.
 7. Thetensioner as in claim 5, wherein the wedge surface comprises anonmetallic material.
 8. The tensioner as in claim 1, wherein thecompressible member comprises a spring.
 9. A tensioner comprising: afirst housing having a first inner surface; a second housing having asecond inner surface and an outer surface, the outer surface slidinglyengaged with the first inner surface; a first compressible memberresisting a movement between the first housing and second housing; apiston having a first end and a second end, the first end being affixedto the first housing and being substantially parallel to a major axis ofthe first housing; a camming body describing a central hole and having asurface slidingly engaged with the second inner surface and the holeslidingly engaged with the second end; and a second compressible memberurging the camming body against the second end, whereby the camming bodyis radially expandable against the second inner surface.
 10. Thetensioner as in claim 9, wherein: the camming body central hole furthercomprises a frustoconcical hole; and the piston second end furthercomprises a frustoconcical shape that cooperatively engages thefrustoconical hole.
 11. The tensioner as in claim 10, wherein thecamming body further comprises: at least one slot, the slot oriented sothe circumference of the camming body is variable in response to amovement against the piston second end.
 12. The tensioner as in claim11, wherein: the camming body surface further describes a pleated form;and the second housing second inner surface further describes a pleatedform that cooperates with the pleated form of the camming body surface.13. The tensioner as in claim 12, wherein: the first housing describes acylinder; and the second housing describes a cylinder.
 14. The tensioneras in claim 13, wherein the camming body surface comprises a nonmetallicmaterial.
 15. The tensioner as in claim 14, wherein the secondcompressible member bears upon the first housing.
 16. The tensioner asin claim 14, wherein: the first compressible member comprises a spring;and the second compressible member comprises a spring.
 17. The tensioneras in claim 14 further comprising: a bearing surface attached to thepiston, the bearing surface extending normally to a piston axis; and thesecond compressible member bears upon the bearing surface.
 18. A dampercomprising: a housing having a housing surface; a wedge having a surfacethat slidingly engages the housing surface, the wedge further describinga hole; a piston having a first end cooperatively engaging the hole; anda compressible member biasing the wedge toward the piston, wherebymovement of the wedge against the first end causes the wedge to radiallyexpand against the housing surface thereby damping a movement of thepiston.
 19. The damper as in claim 18, wherein: the wedge hole comprisesa frustoconcical hole; and the piston first end comprises afrustoconcical shape that cooperatively engages the frustoconical hole.20. The damper as in claim 19, wherein the wedge further comprises: atleast one slot, the slot oriented so the circumference of the wedge isradially expandable in response to a movement against the piston firstend.
 21. The damper as in claim 20, wherein: the wedge surface furtherdescribes a pleated form; and the housing surface further describes apleated form that cooperates with the pleated form of the wedge surface.22. The damper as in claim 21, wherein the housing further comprises acylinder.
 23. The damper as in claim 22, wherein the wedge surfacecomprises a nonmetallic material.
 24. The damper as in claim 23, whereinthe compressible member comprises a spring.
 25. A damper comprising: afirst housing having a first housing surface; a wedge describing a wedgehole and having a wedge surface for slidingly engaging the first housingsurface; a second housing, .the first housing coaxially and slidinglyengaging the first housing; a piston having a first end and a secondend, the first end engaging the wedge central hole and the second endaffixed to the second housing; a first compressible member urging thewedge into contact with the piston first end; a second compressiblemember urging the first housing away from the second housing.
 26. Thedamper as in claim 25, wherein: the wedge hole comprises afrustoconcical hole; and the piston first end comprises a frustoconcicalshape that cooperatively engages the frustoconical hole.
 27. The damperas in claim 26, wherein the wedge further comprises: at least one slot,the slot oriented so the circumference of the wedge is radiallyexpandable in response to a movement against the piston first end. 28.The damper as in claim 27, wherein: the wedge outer surface furtherdescribes a pleated form; and the first housing surface furtherdescribes a pleated form that cooperates with the pleated form of thewedge surface.
 29. The damper as in claim 28, wherein; the first housingfurther comprises a cylinder; and the second housing further comprises acylinder.
 30. The damper as in claim 29, wherein at least the wedgesurface comprises a nonmetallic material.
 31. The damper as in claim 30,wherein: the first compressible member comprises a spring; and thesecond compressible member comprises a spring.
 32. A damper comprising:a first housing having a first housing surface; a second housing havinga second housing surface; a wedge having a wedge surface that coaxiallyand slidingly engages the first housing surface and slidingly engagesthe second housing surface, the wedge further comprising a wedge holesurface describing a hole into which the second housing surface isengaged; a compressible member biasing the wedge toward the firsthousing, whereby movement of the wedge against the first housing surfacecauses the wedge to radially compress against the second housing surfacethereby damping a movement of the first housing.
 33. The damper as inclaim 32, wherein the wedge hole comprises a cylindrical hole.
 34. Thedamper as in claim 33, wherein the wedge further comprises: at least oneslot, the slot oriented so the circumference of the wedge is radiallycompressible in response to a movement against the first housingsurface.
 35. The damper as in claim 34, wherein: the wedge hole furtherdescribes a pleated form; and the second housing surface furtherdescribes a pleated form that cooperates with the pleated form of thewedge hole.
 36. The damper as in claim 35, wherein: the first housingfurther comprises a cylinder; an the second housing further comprises acylinder.
 37. The damper as in claim 36, wherein the wedge hole surfacecomprises a nonmetallic material.
 38. The damper as in claim 37, whereinthe compressible member comprises a spring.
 39. A damper comprising: afirst housing having a first housing surface; a piston having a pistonsurface; a wedge having a wedge surface that coaxially and slidinglyengages the first housing surface and slidingly engages the pistonsurface, the wedge further comprising a wedge hole surface describing ahole into which the piston surface is engaged; a first compressiblemember biasing the wedge toward the first housing, whereby movement ofthe wedge against the first housing surface causes the wedge to radiallycompress against the piston surface thereby damping a movement of thepiston; and a second compressible member biasing the first housing awayfrom the piston.
 40. The damper as in claim 39, wherein the holecomprises a cylindrical hole.
 41. The damper as in claim 40, wherein thewedge further comprises: at least one slot, the slot oriented so thecircumference of the wedge is radially compressible in response to amovement against the first housing surface.
 42. The damper as in claim41, wherein: the wedge hole surface further describes a pleated form;and the piston surface further describes a pleated form that cooperateswith the pleated form of the wedge hole.
 43. The damper as in claim 42,wherein the first housing further comprises a cylinder.
 44. The damperas in claim 43, wherein the wedge hole surface comprises a nonmetallicmaterial.
 45. The damper as in claim 44, wherein: the first compressiblemember comprises a spring; and the second compressible member comprisesa spring.
 46. The damper as in claim 32, wherein the first housingsurface describes a conical shape having an angle in the range of 0°to30°.
 47. The damper as in claim 39, wherein the first housing surfacedescribes a conical shape having an angle in the range of 0°to 30°. 48.A damper comprising: a first member having a first surface; a secondmember having a second surface, the second surface being co-axiallymoveable with respect to the first surface; a frictional member having achangeable circumference slidingly engaging the first surface and thesecond surface; a compressible member urging the frictional memberagainst the first surface whereby a circumference of the frictionalmember is changed resulting in an enlarged frictional contact with thesecond surface.
 49. The damper as in claim 48, wherein the frictionalmember further comprises at least one slot, the slot oriented so thecircumference of the frictional member is changeable.
 50. The damper asin claim 49 further comprising: a second compressible member urging thefirst member away from the second member.